Arkom Kaewrawang

Epitaxial Growth of SrM(00

Strontium ferrite (SrFe12O19) thin films have been deposited on thermally oxidized silicon wafer with Au underlayer by using DC magnetron sputtering system. Crystallization of the strontium hexaferrite phase on Au underlayer is achieved for deposition temperature as low as 475degC. The intensity of (111) diffraction line for Au and that of (00l) diffraction line for strontium ferrite decreases with increasing substrate temperature of underlayer. The maximum of coercivity and remanent squareness ratio in perpendicular direction are 5.7 kOe and 0.86, respectively, at substrate temperature of underlayer of 200degC.

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Strontium ferrite thin films have been deposited on silicon wafer with Al-Si underlayer by using a magnetron sputtering system. The obvious peak for strontium ferrite films deposited on Al-Si underlayer can be observed when substrate temperature is higher than 550degC. The saturation magnetization, coercivity, and remanent squareness ratio of strontium ferrite thin films increase with increasing substrate temperature. The maximum of coercivity and remanent squareness ratio in perpendicular direction are 6.4 kOe and 0.72, respectively, at substrate temperature of 600degC.

) Film on Au(111)

The self-assembled SrM dot array on Au islands has been prepared at various substrate temperatures for underlayer by using DC magnetron sputtering system. C-axis oriented SrM perpendicular to the films can be observed only at substrate temperature for underlayer of room temperature. The intensity of (111) diffraction line for Au and that of (00l) diffraction line for strontium ferrite decreases with increasing substrate temperature for underlayer. The maximum of coercivity and remanent squareness ratio in perpendicular direction are 3.4 kOe and 0.6, respectively, at substrate temperature for underlayer of room temperature.

Properties of Sr Ferrite Thin Films on Al-Si Underlayer

The self-assembled SrM dot array on Au nano-dots has been prepared by using DC magnetron sputtering system without any substrate heating. Then, flash annealing was carried out to crystallize the SrM film. C-axis oriented SrM perpendicular to the films can be observed only at annealing temperature of 800 °C for annealing time of 7 min. The coercivity and remanent squareness ratio in perpendicular direction are 2.8 kOe and 0.72, respectively. The reversal magnetization of SrM on patterned Au nano-dots is closer the Stoner-Wohlfarth model compared to continuous films. The peak of ΔM of SrM film deposited on patterned Au nano-dots is lower compared to SrM deposited on continued Au films.

Structural and magnetic characteristics of SrM thin films on Au dot arrays

Co1−xNix/2Srx/2Fe2O ferrite nanoparticles were prepared using reverse micelle process. Mean particle size of pure ferrite nanoparticles is approximately 9 nm as determined by transmission electron microscopy (TEM). The heating thermograms of samples confirmed that there are no hydroxides in the ferrites fabricated via reverse micelles. Vibrating sample magnetometer (VSM) was employed to probe magnetic properties of nanosized. It was found that with increasing the amount of Ni and Sr in nanosized ferrites, the saturation magnetization decreases. Magnetic dynamics of the samples was studied by the measurement of AC magnetic susceptibility versus temperature at different frequencies. The phenomenological Neel – Brown and Vogel – Fulcher models were employed to distinguish between interacting or non-interacting system. Results show that there is strong interaction between fine particles.